The present invention relates to input/output systems which conveniently combine or integrate a touch switch for data entry and a display device for data output.
It has long been recognized that in many control applications it is desirable to combine a display such as an indicator light, with a switch actuating element essentially superimposed over the display. One common approach is to provide a display lamp or the like and a more or less transparent switch superimposed over the lamp. Advantages of such an approach include immediate feedback to the user at the physical location and moment of contact, savings in required panel area where input and output devices can be colocated, and potential savings in cost where one device serves the functions of two devices at less than the total cost of two devices.
Examples of devices wherein data entry switches and display devices are integrated in various manners and to various degrees are provided by the following U.S. Pat. Nos. 3,207,905--Bray; 3,757,322--Barkan et al.; 4,017,848--Tannis, Jr.; 4,078,257--Bagley; 4,112,429--Tsuha et al and 4,121,204--Welch et al. In each of the devices disclosed in these patents, the data input switches and the display output elements are generally separately identifiable devices with merely a physical connection between the two.
Other integrated entry/display systems have been disclosed wherein there is electrical interaction between the data input elements and the display output elements. One example of this general approach is a technique wherein an electrically conductive area (such as a NESA spot) is applied to the outer envelope of a cold cathode gaseous discharge lamp such as a neon lamp. An exciting voltage just below that which is necessary to trigger conduction is applied to the lamp electrodes. With the display device thus just ready to trigger, an external electric field disturbance occasioned by the proximity of a finger to the NESA spot triggers conduction in the display. In addition to merely providing a visible indication, the conduction may be used to signal other circuitry that the spot has been touched. Thus a single device serves as both a switch and a display.
Another example of an integrated entry and display device with electrical interaction between the display and a touch switch, and one which is particularly relevant in the context of the present invention, is disclosed in the Challoner et al U.S. Pat. No. 3,971,013. The Challoner et al device includes an AC driven gas discharge panel display, and at least one conductive touch key located proximate the display to pick up an AC voltage from a stray field generated by the gas discharge panel display. The Challoner et al device further includes an electrical connection to the conductive touch key for the purpose of detecting a drop in the AC voltage level of the key which occurs due to the proximity of an operator's finger.